The city’s third use of bike boxes shows that SDOT has been experimenting with very different uses for bike boxes. The bike box at 7th and Dearborn in the International District will help cyclists safely turn left into the bike lane on Dearborn headed south west. Unlike the other locations at 12th and Pine and 12th and Madison, this box does not restrict right turns on red.
From what I can tell, the box serves two main purposes that should increase safety. First, the general purpose lane for straight or left turning vehicles was much too wide. A lane that is too wide is more likely to create conflicts, since drivers may be tempted to try to pass if there seems to be enough room. The bike box narrows this lane to a more standard lane width, which makes things easier and safer for people driving as much as it does for people biking.
The other way it helps improve safety is by allowing bikers to pull in front of stopped cars at a red light so they can safely make the left turn into the bike lane. It is dangerous if a person on a bike is trying to turn left while a driver is trying to go straight if that biker is not in front of the straight-going vehicle through the intersection. This bike box helps people on bikes get where they need to be.
My only concern is that people on bikes may ride in the green bike lane when the light is green, putting them to the right of car traffic that may be going straight. This is something to look out for, and I hope SDOT pays attention to this potential danger as they study this bike box usage style.